A nonaqueous secondary battery basically comprises an anode active material, a electrolyte and a cathode active material comprising a lithium-containing transition metal chalcogenide and the like. In the secondary battery using lithium metal as the anode active material, highly active tree-like lithium metal (dendrite) or mossy lithium metal (moss) is formed on the anode during repetition of charging and discharging. When the dendrite or the moss peels off to become in contact with the cathode active material of the battery or when it grows to touch the cathode active material directly, an inner short circuit is produced within the battery. Therefore, such battery, which has insufficient characteristics in charge-discharge cycle, is also in great danger of ignition. In order to solve this problem, proposed are some batteries using lithium alloys such as Al, Al-Mn (U.S. Pat. No. 4,820,599), Al-Mg (Japanese Patent Provisional Publication No. 57(1982)-98977), Al-Sn (Japanese Patent Provisional Publication No. 63(1988)-6742), Al-In and Al-Cd (Japanese Patent Provisional Publication No. 1(1989)-144573). Use of these alloys, however, can not essentially prevent the battery from the production of inner short circuit, because lithium metal is still used for the anode active material.
Recently, as the battery using no lithium metal, proposed are some batteries using carbonaceous materials in which lithium metal or lithium ion can be intercalated and then deintercalated. Such carbonaceous materials are roughly classified into low-graphitized carbon and high-graphitized carbon; the former comprises both an amorphous portion and a crystalline portion, and the latter comprises little amorphous portion and is prepared by heating various low-graphitized carbons at a temperature of higher than 2,400.degree. C. These two carbonaceous materials are clearly different from in terms of properties, so that they are generally distinguished each other and employed for different purposes ("Carbonaceous Material Engineering" by Michio Inagaki, published by NIKKAN KOGYO SHINBUN-SHA (1985)). These carbonaceous materials can be generally obtained as natural products or by burning various organic compounds.
High-graphitized carbon has essentially high charging-discharging capacity (Physical Review B, vol.42(1990), pp. 6424). However, when the high-graphitized carbon is used as an anode active material, the cathode material must be added in an excessive amount at the beginning of charge-discharge cycle because irreversible capacity loss, socalled "exfoliation", occurs (Journal of Electrochemical Society, vol.1,137(1990), pp.2009). Consequently, the charging-discharging capacity of such battery is relatively low. In order to solve this problem, a battery using the combination of the cathode containing no lithium metal and the anode comprising a compound sandwiching lithium metal between graphite layers (lithium metal-graphite-sandwich compound) which is previously prepared is proposed in Japanese Patent Publication No. 62(1987)-23433 and U.S. Pat. No. 4,423,125. However, the lithium metal-graphite-sandwich compound is in danger of ignition and decomposes in the presence of even a slight amount of water, and therefore it is difficult to incorporate such material in a battery. Further, a battery using the combination of the graphite anode and the cathode containing lithium metal is also proposed ("31st Conference of Battery (1990)" pp.97). Even in such battery, however, an excess amount of the cathode material must be added so as to compensate the capacity loss of the exfoliation. Consequently, such battery also hardly brings about increase of the capacity. Further, Japanese Patent Provisional Publication No. 3(1992)-129664 discloses a battery using the combination of the fine fibrous Graphite and the cathode containing lithium metal. However, this battery also has small charging-discharging capacity because the density of the graphite material is very small.
On the other hand, as for carbonaceous material showing low exfoliation, there are proposed many batteries in which low-graphitized carbon is used for the anode (Japanese Patent Provisional Publication Nos. 58(1983)-209864, 61(1986)-214417, 62(1987)-88269, 62(1987)-90863, 62(1987)-122066, 62(1987)-216170, 63(1988)-13282, 63(1988)-24555, 63(1988)-121247, 63(1988)-121257, 63(1988)-155568, 63(1988)-276873, 63(1988)-314821, 1(1989)-204361, 1(1989)-221859, 2(1990)-230660, 1(1989)-274360, 2(1990)-284354, 3(1991)-122974, and WO090/13,924). Even in the above batteries using low-graphitized carbon for the anode, however, the irreversible capacity loss at an early stage of charging which is caused by the exfoliation is still large. Thus, a lithium secondary battery having satisfactory charging-discharging capacity loss has not been produced up to now. In addition, low-graphitized carbonaceous material is known to show charging-discharging capacity lower than that of high-graphitized carbonaceous material (Physical Review B, vol.42 (1990), pp.6424).
As is described above, any of known carbonaceous materials does not have satisfying characteristics needed for an anode active material of a lithium secondary battery, such as reduced charging-discharging capacity loss, increased charging-discharging capacity and assured safety.